Yeah, ETFs are basically a herd-following strategy. When a higher proportion of traders aren't herd-following, this is an efficient strategy. However, as the proportion of herd-followers increases, the information held in a company's stock price increase is less indicative of faith in that company and more of faith in the overall sector. This has led to our current bubble, where everyone is buying stock, so the price goes up, so everyone wants to buy stock.
No clue where the top is going to be, but it feels like this one is going to be uglier than 2008.